2018-11-20T00:11:04ZEcology for sustainable and multifunctional agriculturehttp://hdl.handle.net/11189/6514
Title: Ecology for sustainable and multifunctional agriculture
Authors: Gaba, Sabrina; Alignier, Audrey; Aviron, Stéphanie; Barot, Sébastien; Blouin, Manuel; Hedde, Mickaël; Jabot, Franck; Vergnes, Alan; Bonis, Anne; Bonthoux, Sébastien; Bourgeois, Bérenger; Bretagnolle, Vincent; Catarino, Rui; Coux, Camille; Gardarin, Antoine; Giffard, Brice; Le Gal, Antoine; Lecomte, Jane; Miguet, Paul; Piutti, Séverine; Rusch, Adrien; Zwicke, Marine; Couvet, Denis
Abstract: The Green Revolution and the introduction of chemical fertilizers, synthetic pesticides and high yield crops had enabled to increase food production in the mid and late 20th. The benefits of this agricultural intensification have however reached their limits since yields are no longer increasing for many crops, negative externalities on the environment and human health are now recognized and economic inequality between farmers have increased. Agroecology has been proposed to secure food supply with fewer or lower negative environmental and social impacts than intensive agriculture. Agroecology principles are based on the recognition that biodiversity in agroecosystems can provide more than only food, fibre and timber. Hence, biodiversity and its associated functions, such as pollination, pest control, and mechanisms that maintain or improve soil fertility, may improve production efficiency and sustainability of agroecosystems. Although appealing, promoting ecological-based agricultural production is not straightforward since agroecosystems are socio-ecosystems with complex interactions between the ecological and social systems that act at different spatial and temporal scales. To be operational, agroecology thus requires understanding the relationships between biodiversity, functions and management, as well as to take into account the links between agriculture, ecology and the society. Here we review current knowledge on (i) the effect of landscape context on biodiversity and ecosystem functions and (ii) trophic and non-trophic interactions in ecological networks in agroecosystems. In particular, many insights have been made these two previous decades on (i) the interacting effects of management and landscape characteristics on biodiversity, (ii) the crucial role of plant diversity in delivering multiple services and (iii) the variety of ecological belowground mechanisms determining soil fertility in interaction with aboveground processes. However, we also pinpointed the absence of consensus on the effects of landscape heterogeneity on biodiversity and the need for a better mechanistic understanding of the effects of landscape and agricultural variables on farmland food webs and related services. We end by proposing new research avenues to fill knowledge gaps and implement agroecological principles within operational management strategies.
Description: Article2018-01-01T00:00:00ZApplication of conservation agriculture principles for the management of field crops pestshttp://hdl.handle.net/11189/6512
Title: Application of conservation agriculture principles for the management of field crops pests
Authors: Fanadzo, Morris; Dalicuba, Mvuselelo; Dube, Ernest
Abstract: Worldwide, farmers are called upon to abandon harmful pesticides and
adopt conservation agriculture for improving environmental sustainability, soil
fertility, pest management and farm profits, among other benefits. Whereas the
positive environmental benefits of conservation agriculture are non-questionable,
pest management benefits are still a subject of debate. Abandonment of the plough
and harmful pesticides towards conservation agriculture presented new challenges
to farmers in terms of pest management. Pest problems are frequently reported as
the main yield limiting factor for conservation agriculture in many production
systems of the world, especially among the resource poor farmers. Here we first
review the pest management benefits of conservation agriculture principles, with
special focus on weeds and animal pests. In conservation agriculture, emphasis
should be placed on use of different multiple and varied tactics incorporated into the
cropping system design to avoid damaging levels of pests, thus minimizing the need
for curative solutions. Conservation agriculture embraces integrated pest management,
as it aims to incorporate reduced pesticide applications with cover crops,
conservation tillage and crop rotation to strengthen natural pest control. We show
that effective long term weed management in conservation agriculture systems is
based on an integration of measures for limiting competitiveness of the weeds that
are already in the field and growing with the crop, preventing the introduction of
new weeds, and preventing the multiplication of the weeds that are already there.
Although the abandonment of tillage towards no-till requires an initial investment
on herbicides for weed control, herbicide requirement tends to decline over time
with proper application of conservation agriculture. Proper selection of planting
date, density and spatial arrangement of a crop can maximize the space it occupies
early in the season and put competitive pressure on weeds. Crops can be rotated in
sequences that are not only profitable, but highly effective at breaking animal pest2018-01-01T00:00:00ZChallenges and opportunities for revitalising smallholder irrigation schemes in South Africahttp://hdl.handle.net/11189/6511
Title: Challenges and opportunities for revitalising smallholder irrigation schemes in South Africa
Authors: Fanadzo, M; Ncube, B
Abstract: South Africa is classified as a water-scarce country, and depends on agriculture for food production. The irrigation sector is
the largest consumer of water in the country, accounting for about 62% of water utilisation, but also losing 30–40%. Given
the threat of drought and climate change, efficient irrigation systems have become a necessity, especially in the smallholder
farming sector where most losses occur. Smallholder irrigation schemes (SIS) were developed to improve rural livelihoods
through sustainable food production for food security and poverty alleviation, but these development objectives remain
largely unfulfilled. The objectives of this review were to assess challenges facing SIS and explore opportunities for revitalising
the schemes. The focus was on government policy and strategies to support smallholder farmers. A review of government
policy showed that although the needs and interests of smallholder farmers are high on the national agenda, there is
insufficient financial support to the sector, suggesting that smallholder agriculture is not really seen as a potential driver of
the economy. The core focus of the government on repairing irrigation infrastructure while neglecting the soft components
relating to capacity building has partly been blamed for the failure of SIS in South Africa. Capacity building is one of the
missing links in smallholder irrigation development and many failures have been attributed to lack of adequately trained
farmers and extension staff, particularly in irrigation water management. Land tenure insecurity has been singled out as a
major institutional challenge leading to poor performance of irrigation schemes. The diversity of schemes means that different
kinds of interventions are needed to respond to varying farmers’ needs, resources and agricultural contexts. These findings
point to the need to balance the soft and hard components of the irrigation schemes for sustainability. It is therefore evident
that the government needs to review its priorities in revitalisation of SIS. Land tenure policies allowing increased access to
arable land need to be developed urgently, together with the promotion of alternative cropping systems that are suitable for
the smallholder farming sector.2018-01-01T00:00:00ZOptimisation of parameters for spectroscopic analysis of rare earth elements in sediment sampleshttp://hdl.handle.net/11189/6477
Title: Optimisation of parameters for spectroscopic analysis of rare earth elements in sediment samples
Authors: Makombe, Martin; Somerset, Vernon; van der Horst, Charlton; Silwana,Bongiwe; Emmanuel, Iwuoha
Abstract: The rapid demand for rare earth elements (REEs) in recent years due to increased use in
various technological applications, agriculture, etc. has led to increased pollution and
prevalence of REEs in the environment. Therefore, monitoring for REEs in the aquatic
environment has become essential including the risk assessment to aquatic organisms.
Since direct determination of REEs in sediment samples prove difficult at times, due to
low concentrations available and complex matric effects, separation and enrichment steps
are sometimes used. In this work, various REEs were determined employing wet acid
digestion and lithium metaborate fusion in our optimised analytical technique. A comparison
of the two analytical techniques was also made. The results obtained from the
optimised ICP-OES radial view technique were in 5% agreement with the ICP-MS results
from the same samples. The accuracy of the method was checked with the geological reference
material GRE-03 and found to be in reasonable agreement. We demonstrated that
there is a consistent relationship between the signals of the REEs and nebuliser gas flow
rates, plasma power and pump speed. The detection limits for all the REEs ranged from
0.06 mg L-1
Yb to 2.5 mg L-1
Sm using the ICP-OES fusion technique.2017-01-01T00:00:00Z